This invention relates to a cutter blade device of a mowing machine including a flexible cord, such as a nylon cord, wound and held in the machine to serve as a cutter for cutting grass.
Generally, the cutter blade device of the mowing machine of the type described is mounted to a lower end of a drive shaft extending through an operating rod of the mowing machine and driven for rotation by a relatively small internal combustion engine located rearwardly of the operating rod. In one type of cutter blade device known in the art, a spool having cords wound thereon is fitted in a casing, and an inertia shifter which is rotatable and movable in the direction of the axis of rotation of the casing and the spool is disposed along an inner periphery of the casing, and outer end portions of the cords are drawn out from the casing through openings formed in the inertia shifter to perform a mowing operation. When the outer end portions of the cords have been worn out after use, the machine is rapidly caused to swing to rotate the inertia shifter through a predetermined angle to thereby enable the cords to be further payed out from the casing automatically. In a construction in which the inertia shifter is kept in engagement with the casing by utilizing the behavior of the cords to become straight under the influence of centrifugal forces during operation, the positions in which the cords are payed out of the spool and positions in which the openings are formed in the inertia shifter preferably remain unchanged relative to each other. Misoperation of the inertia shifter would tend to occur when a large spool is used to wind a plurality of cords for improving operation efficiency.